74 FIRST LESSONS WITH PLANTS 



some compositous flowers the florets are reduced 

 to two or three, or even to one! 



SUGGESTIONS. Is the bud at the right in Fig. (J7 a flower 

 closed up, or one which has not yet opened ? Are the stems of 

 the dandelions which bloom first in the spring shorter than those 

 which bloom later ? Do the flowers close at night and in dull weather ? 

 How long a period of sunshine is necessary to open the flowers ? 

 Does a flower open more than once ? Does the head (or involucre) 

 ever close up after it has gone to seed ? What time is required 

 for the flower stem to straighten up and to reach its full height ? 

 How many rows of bracts or scales are in the involucre ? Do the 

 positions of these bracts change from flowering-time to seeding- 

 time ? How far may a dandelion seed travel in the wind ? Do 

 dandelion plants vary much in size and shape of leaves (compare 

 Fig. 68 j? Is the variation associated with vigor of plant, richness 

 and moisture of soil, or other conditions ? At what seasons are 

 dandelions most abundant ? Do they ever bloom in fall or winter ? 

 How long does a dandelion plant live I Upon what kind of soil 

 does it thrive be'st ? 



XV. CROSS - FERTILIZATION 



91. We have found (58) that the purpose of 

 the flower is to produce seeds ; these seeds can- 

 not be formed without the aid of pollen; compara- 

 tively few flowers are perfect and also synanthous 

 (or simultaneous) in the maturation of pistils and 

 stamens, and very many flowers are imperfect. 

 It would seem to follow, therefore, that cross -fer- 

 tilization is the rule, and we infer that it must 

 result in some decided benefit. 



92. The simplest means by which cross -fertili- 

 zation is enforced is by dichogamy, or the different 



